This invention is directed to a segmented head seal for a cup packaging machine wherein individual sealing blocks are linked together to form a composite segmented head seal.
For use in the fast food and other industries, packaging cups have been developed for containing individual servings of condiments and other products. These cups allow for packaging, storing and dispensing of premeasured protected amounts of these condiments or other food products. Typically these cups are utilized to dispense individual servings of catsup, mustards, sauces, salad dressings and other similar type products.
These packaging cups include a cup body which has a product reservoir surrounded by a lip. A cover or seal is sealed to the lip to seal the contents within the reservoir of the cup. To use the cup, the seal or cover is pealed back off of the lip of the cup exposing the contents in the reservoir.
Generally, the body of these cups, that is the portion of the cups excluding the cover or seal, is formed out of a resilient material as, for instance, polyethylene utilizing vacuum forming techniques. In forming the cups a sheet of polyethylene is placed over a die and the sheet vacuum formed into the die forming a matrix of joined cup bodies in the sheet. Generally the matrices of joined cup bodies are in 4 by 4 or 5 by 5 matrices whereby each perform sheet will ultimately yield 16 or 25 individual cups when they are separated from one another.
The cups are filled and sealed while they are still attached to one another in the matrix of joined cup bodies. Thus, a material sheet having matrix of preformed cup bodies formed therein is loaded onto a packaging machine, the cups are filled then sealed and then the individual cups are separated one from another.
Typically since the above referred to cups are formed by vacuum forming, there can be irregularities in the thicknesses of the lips of the cup resulting from the vacuum forming process. This arises because there may be uneven stretching during vacuum forming of the polyethylene sheet resulting from the stresses at the edges of the sheet being different than the stresses at the center of the sheet.
Known head seals for cup packaging machines, hereinafter referred to as preform cup machines, utilize a solid sealing head. This head is sized and shaped to contact one half of a matrix of a sheet of cup bodies as, for instance, in a 4 by 4 matrix by simultaneously contacting and sealing the cover onto 8 cup bodies at a time. Normally this is done by sealing two rows of 4 columns each across the width of the sheet of cup bodies, advancing the sheet of cup bodies underneath the head seal and sealing the remaining two rows of 4 columns each.
Because the thicknesses of the cup lips can vary within a particular sheet of joined cup bodies, imperfect seals can be formed in individual cups. These cups are then subject to leakage. Leaking cups, of course, have to be discarded. Generally a leaking cup will not be detected until pressure is applied to the cup. This often happens during shipping when the cups, which are packaged in bulk, are jostled against one another. A leaking cup not only loses its contents and thus becomes useless but it also contaminates the outsides of other cups and these then also have to be discarded because of the deposits located on them.
The above referred to preformed cup machines are engineered for high speed operation and high volume production. As with any machine ultimately wear will occur. Generally since the head seals are supported by the sides and large pressures are utilized for sealing the covering material to the cup body, wear of the head seal will first occur in the center of the head seal. With a head seal which has started to wear, irrespective of whether or not the cup bodies are perfectly formed, ineffective seals can be formed because of the differences of pressure exerted by a worn head seal over the center cups opposed to the edge cups on a sheet of joined cups. This leads to premature failure of these one piece solid head seals.